Space based laser weapons and other based laser systems which are required to focus the laser beam on targets or receivers at long distances necessitate the final optic to have a correspondingly large diameter. Also, if diffraction limited performance is desired and a conventional mirror or lens is to be used, then the optical surfaces of these mirrors or lens must be accurate to a fraction of a wavelength of the laser light being used.
The diameter of the exit aperture of the antenna or telescope can be determined from the range and the desired spot size at the target. For example, the diameter D is given by: ##EQU1## where .lambda. is the laser wavelength, .rho..sub.T is the minimum radius of the spot to be produced at the target and R is the distance to the target. In some applications, the diameter may need to be as large as 20 meters. Such large good quality optics do not exist, and even if one were to be made, it would take many years to manufacture, and it would weigh so much that it could not be placed in space. For example, the mirror of a 200 inch (about 5 meters) telescope requires at present more than four years to manufacture and it weighs too much.
For defense application, many such large optics are required, and for other applications more than one will be needed. Because of this, much work has been done and is being done to develop light weight large optics that can be erected in space. Although some progress has been made, these devices are still heavy, costly, too small, and require too long to produce. Also, the optical quality needed cannot be obtained nor maintained over the required diameters.
Therefore, it is an object of this invention to provide a light weight large optics for mounting in outer space.
Another object of this invention is to provide a large optics that is light in weight due to its using gas as a medium for the lens.
Another object of this invention is to provide a relatively light weight lens that can be made of varying size and therefore adaptable to different applications.
Still another object of this invention is to provide a large erectable optics device that can be produced in a small amount of time.
Other objects and advantages of this invention will be obvious to those skilled in this art.